The present invention relates to an asphalt water-proofing material comprising a core made of composite material including a non-woven fabric and a woven or knitted fabric connected together by needle-punching, said core being impregnated with petroleum asphalt.
There are various types of method for constructing water-proofing structure. The asphalt water-proofing method, among of them, has many advantages over the other methods, such as sheet water-proofing method (which method has a defect in that it tends to produce voids in the connecting area, which cause separation of the water-proofing layer for the substructure or adversely affect the life of the water-proofing property of the water-proofing structure) or method of applying water-proofing material or film on the substructure (which method has such defects that it is difficult to form a water-proofing layer having substantial thickness or uniform thickness), from the reasons that the asphalt water-proofing method provides excellent water-proofing property and also provides high reliability and durability owing to its good quality of material and easy workability and furthermore this method is advantageous from the economical point of view. Accordingly, the asphalt water-proofing method is now widely used, for example, in the field of building construction, to form a water-proofing structure for building roof, wall of kitchen or lavatory or the like, or in the field of earth working, to construct a water-proofing structure for inside or outside wall of underground structure, wall of open-air pool, drainage canal or irrigation canal or the like.
The asphalt water-proofing method includes the steps of successively laying a plurality of asphalt roofing layers upon a substructure to form a water-proofing structure integrally connected by asphalt, and the water-proofing property of this structure basically depends upon the water-tightness of the asphalt. The water-proofing structure made of only asphalt is liable to produce cracks therein owing to drying or shrinkage of the substructure such as concrete slab or the like and such cracks may lead to cause breakage in the asphalt owing to fatigue produced by the repetitive movement at the cracks. The asphalt water-proofing structure has a further disadvantage in that it tends to harden at the lower temperature while it tends to flow at the higher temperature. In order to avoid such disadvantage, it has been proposed to provide a roofing which includes a porous core of reinforcing material such as paper or non-woven fabric made of natural, synthetic, glass or other fibres, said core being impregnated with petroleum asphalt.
A roofing of this kind which includes the paper core is usually prepared by impregnating the core with straight asphalt and then coating said impregnated core with blowing asphalt. This roofing, however, lacks stretching property so that it may easily produce breakage by a slight crack caused in the substructure and a slight relative motion in vertical direction between the cracked portions, and consequently the roofing of this type has very low reliability in its water-proofing function.
Another roofing of this kind, which is called "stretch-roofing", comprises a core made of non-woven fabric in which synthetic filaments are arranged in a layer in random fashion to form a web, to which is applied an adhesive material (usually, emulsion of synthetic resin) such as by spraying to fix the crossing points of the fibres. This roofing has general properties of high tensile strength at the initial stage as well as at the maximum elongation and low stretchability, owing to the fixing of the fibres at their crossing points, as described above, and consequently it has high rigidity and low resistance to crumpling effect and lacks restoring property. Although it has higher adaptability to cracks caused in a substructure than that of an asphalt roofing having paper core, it is low in its fatigue-resistant property and incomplete in its durability as a water-proofing layer.
Another asphalt roofing has been known, which includes a bulky non-woven fabric having substantial thickness, for example 4 mm, which is prepared by applying needle-punching process to a mass of endless filaments of polypropylene thereby interlocking these fibres together (see, U.S. Pat. No. 4,035,544). This asphalt roofing has high tensile strength, such as 15.0 kg/10 mm width or more, and high stretching ratio which is higher than five times of that of the conventional asphalt roofing. Furthermore, it is superior in its crack-resistant and crumpling-resistant properties. Sometimes thinner asphalt roofing may be required, depending on the purpose or mode of using the asphalt roofing. In such a case, if the thickness of the non-woven fabric of the core was decreased (for example, to 1.5 mm thickness), the filaments could not be satisfactorily interlocked together by the needle-punching process alone, so that there remain such disadvantages that the core is liable to cause wrinkles or shrinkages during asphalt impregnating step and the roofing thus produced has low tensile strength although it has high elongation.